A General Approach to the Analysis of Fatigue Cracks in Lubricated Contacts

Lead Research Organisation: Imperial College London
Department Name: Dept of Mechanical Engineering


In recent years there has been noticeable appreciation of the importance of failure mechanisms which affect the performance of the most critical assemblies, whose components undergo mutual contact interactions. In particular, most of the complex engineering products such as bearings, gas turbine blades/shafts, gears, railways, bolted flanges, car engines, etc. could not operate without contact and frictional interfaces. Therefore the assessment of tribological performance (i.e. how the material strength of couplings if affected by the presence lubricants, friction and wear) of these assemblies is a must for any industrial setting.Let us consider bearings as an example application. They are mechanical components used to reduce friction and provide load support for rotary or linear equipment. A single bearing failure can cause hours of downtime, including the identification and replacement of the failed component. For this reason, companies around the world have spent a vast amount of money and resources on different types of predictive maintenance technology. This suggests that fundamental research on the main phenomena responsible for such failures needs to be carried out.The proposed work will attempt to address the root causes of material failures in the presence of lubricated contacts. The role of fluid, according to some experimental observations, experience gathered from engineering practice, and the results of the theoretical analyses, is often regarded as the main contributor to catastrophic crack growth. The origin of cracks induced by the rolling/rubbing of contacting pairs will be studied and the fluid/solid interaction which is deemed as responsible for the propagation of such cracks will be investigated. Furthermore, robust experimental techniques will allow monitoring and measuring the presence of fluid within cracks generated during rolling contacts and subsequent crack growth to failure.A properly managed research programme will provide valuable feedback about how a component performs when subjected to contact loading under different working conditions. It will uncover information for improvements that prevent future failure. Rigorous root cause determination might lead to improvements that yield:(a) Greater safety(b) Improved design and reliability(c) Greater efficiency(d) Reduced maintenance(e) Reduced life-cycle costs


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Description We have for the first time developed a methodology to study fluid/solid interactions to describe the evolution of cracks in lubricated contacts, which are of relevance to rolling element bearings, railways systems and many other lubricated systems subjected to contact fatigue.
Via developing new experimental methods and modelling techniques we have successfully predicted the conditions responsible for failures in some critical components and developed techniques and palliatives to reduce their occurrance.
Exploitation Route The techiques developed have now been incorporated in design strategies of rolling element bearings (SKF) and railways (Network Rail). Further research is currently been pursued by the PI thanks to the award of the SKF University Technology Center to his group in 2010.
Sectors Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology,Transport

Description The techniques developed to capture fluid/solid interactions within cracks in rolling and sliding contacts have been exploited by companies to develop design and predictive tools. Procedures for improved material and lubrication solutons have now been incorporated in design strategies of rolling element bearings (SKF) and railways (Network Rail). Further research is currently been pursued by the PI thanks to the award of the SKF University Technology Center to his group in 2010.
First Year Of Impact 2010
Sector Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology,Transport
Impact Types Economic

Description "iBETTER" - "Improved Bearing Technology Through European Research"
Amount £1,486,940 (GBP)
Funding ID 612306 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start 10/2013 
End 09/2017
Description Engine Efficiency Benefits from Surface Texturing
Amount £130,000 (GBP)
Organisation Ford Motor Company 
Sector Private
Country United States
Start 01/2016 
End 01/2017
Description Platform Grant
Amount £1,024,467 (GBP)
Funding ID EP/G026114/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2009 
End 12/2013
Description Royal Swedish Academy of Sciences
Amount 100,000 kr (SEK)
Funding ID Personal Prize 
Organisation Royal Swedish Academy of Sciences 
Sector Charity/Non Profit
Country Sweden
Start 09/2007 
End 09/2007
Amount £1,800,000 (GBP)
Funding ID Industrial Funding for the establishment of a University Technology Centre 
Organisation SKF 
Department S.K.F. Engineering & Research Services B.V
Sector Private
Country Netherlands
Start 01/2010 
End 12/2019
Title BEM_crack 
Description Developed a BEM code for crack propagation 
Type Of Material Improvements to research infrastructure 
Year Produced 2011 
Provided To Others? Yes  
Impact A couple of researchers have applied it to study rolling fatigue crack propagation at SKF 
Description Railways Contact Modelling 
Organisation Network Rail Ltd
Country United Kingdom 
Sector Private 
PI Contribution Developed models to study contact and lubrication isses in railways
Collaborator Contribution Studentship and data
Impact Main outcomes: - PhD on damage in switches and crossings - Gained important knowledge of failure mechanisms in these systems.
Start Year 2009
Organisation SKF
Department S.K.F. Engineering & Research Services B.V
Country Netherlands 
Sector Private 
Start Year 2007
Description University of Modena and Reggio Emilia 
Organisation University of Modena and Reggio Emilia
Country Italy 
Sector Academic/University 
PI Contribution A collaboration has been established with the University of Mdena and Reggio Emilia to develop algorithms to study fluid film lubrication in teh presence of cavitation. Three visiting researchers have now been hosted at Imperial College and a number of Conference papers and two journal articles have now been published.
Start Year 2007